Abstract: A pot experiment was conducted to investigate the contribution of alfalfa (Medicago sativa), smooth brome (Bromus inermis), and sludge microbes to the remediation of polycyclic aromatic hydrocarbons (PAHs). After 5 months, the total removal rate of polycyclic aromatic hydrocarbons (PAHs) by sludge microbes was 20.52% in the absence of forage grass, and the removal rate of PAHs with different rings was as follows: six rings≈four rings≈three rings>five rings≈two rings. The total removal rate of PAHs by grass-sludge microbes was 83.74% (alfalfa) and 78.73% (smoothbrome). Therefore, the addition of a grass significantly increased the average PAH removal rate by almost three times compared with that of sludge microbes alone. The highest degradation rate was for the six-ring PAHs. In the absence of sludge microbes, the degradation rate of PAHs by alfalfa and smoothbrome was 63.22% and 58.21%, respectively (on average, 33.90% less than that of the grass-sludge microbes combination).The grasses showed the highest PAH removal rate for five-ring PAHs. Further analyses of the contribution rates of grass and sludge microbes to PAH degradation showed that 1.35% of PAHs was removed by direct absorption, 24.67% by microbes, and 79.46% through grass-sludge microbial interactions, transpiration, and the effects of root secretions. The treatments were ranked from highest sludge alkaline phosphatase activity to lowest as follows: non-sterilized sludge+alfalfa treatment (J+M)≈non-sterilized sludge+smooth brome treatment (J+W)>non-sterilized sludge treatment (J)>sterilized sludge treatment (CK) (P<0.05), consistent with the order of the treatments based on PAHs degradation. In conclusion, the use of grass and sludge microbes was more effective for removing PAHs from contaminated sludge than either grass or sludge microbes alone. The combined action of grass and microbes removed PAHs as a result of their interactions and transpiration.